Design and numerical investigation to visualize the fluid flow and thermal characteristics of non-axisymmetric convergent nozzle

Abstract

In this paper, numerical simulations are conducted to visualize the fluid flow and thermal characteristics of a non-axisymmetric convergent nozzle. The novel design methodology is based on curve-fitting approach. The curves used for designing the nozzle are based on a combination of fifth and third order polynomial at upper and lower surfaces respectively. The computations are performed using commercially available computational fluid dynamics (CFD) tool ANSYS CFX®. Firstly, mesh independence analysis are carried out. Then, numerical simulation is further validated for medium and low-pressure helium by comparing it with the available experimental data. Thereafter, an exhaustive analysis is carried out to compare the fluid flow behavior inside the nozzle for two cryogenic fluids, nitrogen and helium at three different inlet pressure and temperature. The fluid flow pattern, pressure, velocity, Prandtl number, static enthalpy, Reynolds number, eddy viscosity, etc. are identified at various positions. The Mach number and temperature at the outlet of the nozzle is the key feature of this analysis which satisfies the criteria for a nozzle which is used for the high, medium and low-pressure turbine. The analysis provides a better understanding of the further improvement of the design methodology or performed an experiment. The designed nozzle has a tremendous effect on the fluid flow behavior and suitable for impulse type turbine with a small amount of reaction used in a turboexpander. The work proposes a new design methodology for designing a non-axisymmetric airfoil convergent nozzle of rectangular cross-section.